The present invention provides compositions and methods for modulating the expression of PLML. In particular, this invention relates to compounds, particularly oligonucleotides, specifically hybridizable with nucleic acids encoding PLML. Such compounds have been shown to modulate the expression of PLML.
Despite the relatively constant osmolarity in mammals, volume-regulatory transporters have important roles in mammalian physiology because changes in cell volume also serve to signal cell growth and differentiation (O""Neill, Am. J. Physiol., 1999, 276, C995-C1011). An increase in cell volume in mammals is the signal for activation of chloride currents mediated by volume-activated chloride channels (Nilius et al., Gen. Pharmacol., 1996, 27, 1131-1140).
One such chloride channel is phospholemman, a small transmembrane protein first discovered in canine cardiac sarcolemmal vesicles in 1991 (Palmer et al., J. Biol. Chem., 1991, 266, 11126-11130). Human phospholemman has since been found to be widely distributed in human tissues with the highest expression in skeletal muscle and heart, suggesting a functional role in muscle contraction (Chen et al., Genomics, 1997, 41, 435-443). Phospholemman""s role as a chloride channel was suggested following the observation that phospholemman expression in Xenopus oocytes induces a chloride-selective current (Moorman et al., J. Biol. Chem., 1992, 267, 14551-14554).
Shortly thereafter, a protein with a sequence related to phospholemman was discovered in murine mammary tumors whose expression is initiated by the transgenic oncogenes c-neu and v-Ha-Ras but not c-myc (Morrison and Leder, Oncogene, 1994, 9, 3417-3426). Subsequently, this phospholemman-like protein was found to be expressed in human breast tumors and, like phospholemman, can induce chloride conductance when expressed in Xenopus oocytes. This indicates a role for the phospholemman-like protein in regulation of chloride flux as a chloride channel or channel regulator (Morrison et al., J. Biol. Chem., 1995, 270, 2176-2182).
The phospholemman-like protein expressed in breast tumors (PLML) is also known as mat-8 (mammary tumor, 8 KDa). In addition, it was recently named FXYD3 to highlight its classification as a member of the FXYD gene family of small ion transport channels or regulators named in recognition of the invariant amino acid residues Phe-X-Tyr-Asp in the signature motif (Sweadner and Rael, Genomics, 2000, 68, 41-56).
Since PLML is a marker specific for tumor cells transformed by Neu or Ras, it may be a required component for Neu and Ras transformation and its expression and function critical for maintenance of the transformed state (Morrison and Leder, Oncogene, 1994, 9, 3417-3426; Morrison et al., J. Biol. Chem., 1995, 270, 2176-2182). If PLML function is found to be a critical component of certain classes of oncogenic events, it may prove to be an ideal target for therapeutic intervention in treatment of breast cancer because it is clear that PLML is not expressed by all cell types and thus does not perform a housekeeping function common to all cells (Morrison et al., J. Biol. Chem., 1995, 270, 2176-2182).
The DNA sequence encoding mat-8 (PLML) is disclosed in U.S. Pat. No. 5,728,597 as are methods of detecting and treating breast cancer (Morrison and Leder, 1998).
Antisense technology is emerging as an effective means of reducing the expression of specific gene products and may therefore prove to be uniquely useful in a number of therapeutic, diagnostic and research applications involving modulation of PLML expression.
The present invention provides compositions and methods for modulating the expression of PLML.
The present invention is directed to compounds, particularly antisense oligonucleotides, which are targeted to a nucleic acid encoding PLML, and which modulate the expression of PLML. Pharmaceutical and other compositions comprising the compounds of the invention are also provided. Further provided are methods of modulating the expression of PLML in cells or tissues comprising contacting said cells or tissues with one or more of the antisense compounds or compositions of the invention. Further provided are methods of treating an animal, particularly a human, suspected of having or being prone to a disease or condition associated with expression of PLML by administering a therapeutically or prophylactically effective amount of one or more of the antisense compounds or compositions of the invention.